Crunch time is coming for Red Sox first baseman Mike Napoli. His team is headed to the World Series, and he was a hero of the American League Championship Series, with two home runs and a .300 average.

Napoli wants to repeat that performance on baseball's biggest stage, of course, because he wants to win. But, at the conclusion of the World Series, Napoli will be looking for another kind of victory, when he enters free agency for the second time in a year.

This time around, though, Napoli has proof that the hip issues that turned his three-year, $39 million deal with the Red Sox into a one-year contract worth $5 million plus incentives that pushed it up to $13 million, won't be holding him back.

"It was very frustrating when I was trying to sign," Napoli said. "I waited seven years for free agency and then got an opportunity, and it got taken away because of something I didn't even know I had and had never had any pain from."

That condition is avascular necrosis (or AVN) -- a degenerative hip condition discovered during the routine physicals that accompanied Napoli's contract negotiations last winter. With AVN, a lack of blood supply causes the death of bone tissue. In Napoli's case, the blood flow into his hip sockets is restricted. Left untreated, it can cause persistent pain and stiffness and reduced range of motion. If the hip bone becomes necrotic, the condition can cause pain to radiate from the hip into the groin and down the leg. In the worst-case scenario, the femoral head can become so brittle it collapses. NFL star Brett Favre played nearly two decades with AVN, but it was also the condition that ultimately ended Bo Jackson's dual-sports careers.

Mike Napoli went 6-for-20 with two doubles and two homers during the ALCS. (Getty)

Napoli, though, has been completely asymptomatic. He's managing his hip issues with osteoporosis medication, which slows the rate of bone degeneration and maximizes healthy bone production. He's had MRIs every three months since January, and they have shown no increase in bone loss.

"You're in a quandary when you find AVN, because it's unpredictable," said Dr. Bryan Kelly of the Hospital for Special Surgery, who performed hip surgery on the Yankees' Alex Rodriguez. "You don't know if the bone tissue is going to be stable or if it will collapse and leave the player unable to play at all.

"If a large part of the femoral head has avascular necrosis, the team doctor would be concerned, and for Napoli, it became a scarlet letter on his medical chart. But if he's had repeated good MRIs, I wouldn't worry about it. He's proven it's stable and he can play with it."

When Napoli drove a 92-mph Anibal Sanchez fastball 460 feet into the second row of the center-field shrubs at Comerica Park in the second inning of Game 5 of the ALCS, he hardly looked like a man afflicted. During the series against the Tigers, Red Sox manager John Farrell also praised Napoli's defense at first base, citing a number of balls Napoli picked out of the dirt to secure double plays, and called Napoli "the best instinctual baserunner" on the team.

During the regular season the sometimes streaky Napoli had a .259 average and .482 slugging percentage and was second on the team with 23 home runs and 92 RBIs. He earned $8 million in incentives for hitting benchmark numbers for plate appearances and days spent on the active roster after notching 578 plate appearances and not spending a day on the DL all season.

"I'm a little more confident about negotiating a contract now that I've shown all year that my hips aren't an issue, but I'm sure I'm going to have to go through all the steps again, with all the MRIs and talking to doctors."

-- Mike Napoli

"I'm a little more confident about negotiating a contract now that I've shown all year that my hips aren't an issue, but I'm sure I'm going to have to go through all the steps again, with all the MRIs and talking to doctors," Napoli said. "They're always going to say, 'What if?' But what if I got hit in the hand or got hurt in some other way that had nothing to do with my hips? So many things can happen, but I don't feel like my hips are a problem."

Prior to signing with the Red Sox, Napoli did have pain from a labrum tear in his left hip that he's had since his time with the Angels, and it was the investigation of that issue which led to his diagnosis of AVN.

When Napoli was catching, the labrum was an issue, and the pinch he felt while moving quickly in and out of a squat was a constant reminder.

"When I caught, it would rub and it'd be pinching so bad that the whole side of my leg would be hurting," he said.

That pain was managed with cortisone shots throughout his time in Texas, but once Napoli stopped catching, the pain went away.

Still, labrum tears can be scary for baseball players -- and baseball doctors -- because they limit the ability to get proper hip rotation. Remember how, for a while before his surgery, Rodriguez was late on his swings? But many people can also have labrum tears and be pain-free, as Napoli has been -- despite his AVN -- since moving primarily to first base.

"We're happy for Mike," Farrell said. "He has physically responded to the treatment he began last offseason and has had follow up imaging just to monitor [the situation]. The treatment is working. It has not allowed any further deterioration, and the way he's performed is everything that we anticipated. [He] has been a main contributor to our entire year."

After the World Series, Napoli will find out what the Red Sox are willing to give him in return.

Lindsay Berra is a reporter for MLB.com. Follow her on Twitter at @lindsayberra. This story was not subject to the approval of Major League Baseball or its clubs.